Electric power from solar and wind power generators is not necessarily available at the same time when a need of electric power is present in a public power grid to which the power generators are connected. Rather, the supply of high electric power by the power generators, like for example by solar power generators at noon time, may coincide with a surplus of electric power already present in the connected public power grid. This may have the result that the output power of the power generators has to be curtailed and thus electric power gets lost which would be available at no additional cost.
If in a local power grid comprising a power generator more electric power is produced than consumed and the excess electric power is fed into a public power grid at one time, whereas more electric power is consumed than produced and the missing electric power is taken of the public power grid at another time, the public power grid essentially serves as a buffer for electric power. This buffer capability causes considerable cost to the operator of the public power grid for which he will ask for compensation.
By now, the supply price of electric energy already extremely depends on the point in time at which the electric energy is supplied. Power tariffs depending on the supply time will thus more and more also be offered to private consumers.
Against this background, a load management is desirable which is optimized with regard to the supply of electric power actually present and which fulfills the aims of a high local consumption of electric power at the location where the electric power is produced by solar or wind generators, i.e. achieving a minimum utilization of a connected public power grid.
A method and an apparatus for optimizing a chronological development of consumption of electric power by a group of different consumers with regard to a supply of electric power which includes electric power from at least one wind or solar generator and a local power grid including such an apparatus are known from DE 10 2008 037 575 A1. By means of a computer based method, the operation of consumers and energy sources of a local system are monitored, controlled and optimized. Solar and/or wind power generators belong to the local system as stationary power sources. Part of the known computer based method is making a plan for an optimized utilization of energy in the local system based on information which includes the prospective overall power consumption by the consumers and the prospective power supply by stationary power sources at future points in time. The prospective overall power consumption at the future points in time is calculated from the measured power consumption of one or several of the consumers. For calculating the power which is supplied by the stationary power sources at the future points in time, the prospective environmental conditions at these points in time are considered. In the diagrams of DE 10 2008 037 575 A1, the power consumption is plotted in blocks covering a duration of 40 minutes, and changes of the power consumption do not occur earlier than after two hours.
A method of optimizing a chronological development of consumption of electric power by a group of different consumers with regard to a supply of electric power which includes electric power from at least one wind or solar power generator is also known from DE 10 2009 010 117 A1. The aim here is to level the electric power consumed by a group of different loads. In a first step, an uncontrolled consumption of power is determined over a defined period of time related to the calendar. In a second step, an average value is calculated from this uncontrolled consumption of power which is used as a preset target value during a similar future period of time. Different priorities are assigned to the consumers, and the consumers are operated according to their priority so that their presently consumed overall electric power does not exceed the target value. With this method, the consumption of electric power may be levelled, and this may, depending on tariff conditions, be economically advantageous for the operator of the local power grid. In the known method, maximum switch-off periods of individual loads, like for example a heat pump for heating a building are registered. Heat or cold generating consumers are purposefully operated during low load periods, so as to store heat or cold for succeeding high load periods in which these consumers are preferably not additionally operated. The operation of dishwashers and washing machines shall preferably also take place during low load periods. Thus, a low priority is assigned to such consumers. On the other hand, consumers like lamps or stoves get a high priority as the need of light or cooking energy depends on momentary desires to an extremely high extent. Further, it is considered that the power consumed by individual consumers varies depending on the progress of their operation cycles. Considering, for example, a washing machine, once switched on it will be in operation for up to two hours and more. The power demanded by the washing machine is comparatively high when water is heated up to a preset washing temperature. For subsequently moving the washing drum, however, only little power is needed. The present consumption of electric energy is measured at intervals of 1, 3 or 5 minutes in the known method. These intervals of time are adapted to a price calculation period of 15 minutes for which an average consumption value is transferred to the operator of the connected public power grid. The price to be paid for the power consumed is calculated based on these average consumption values. In the known method, a local generation of power by solar or wind power generators is considered. If the locally generated power is higher than the locally consumed power, the excess or surplus power is fed into the connected public power grid. Vice versa, missing power is taken from the public power grid.
So-called intelligent electrical sockets for connecting electric consumers are known from DE 44 25 876 A1. The consumers are controlled, i.e. they are switched on, switched off and/or dimmed, via a BUS system which uses the power mains as a transmission medium. Via an additional interface connector, sensors may be connected to the intelligent electric socket and interrogated via the BUS system.
An analyzing apparatus for current consumers in which at least one consumer comprises a unit which is suited for identifying the power consumption of exactly this one consumer and to provide it as information is known from DE 20 2008 009 128 U1. The analyzing apparatus comprises a receiver for the information provided by the at least one consumer. This receiver is suited for separately recording, processing and calculating results according to predetermined algorithms from information from each of the consumers upon switching on and/or switching off the consumers individually. The information transmission takes place via the power supply lines at more than 50 Hz, preferably more than 100 Hz, i.e. at more than 50 b/s or more than 100 b/s. The analyzing apparatus may determine and output the individual power consumption of each consumer and reduce the power supply to this current consumer or switch it on and off. In the known analyzing apparatus, the individual identification of the individual consumers is achieved by means of their individual consumption behaviour. Thus, inductive and capacitive consumption patterns of each consumer, in a figurative sense, comprise the properties of a finger print. This electric finger print consists of a switch-on current pulse and of harmonic waves imprinted in the local power grid. If these harmonic waves are analyzed, it is—due to their individual composition—possible to identify the causing consumer. Thus, by means of an identification of the individual consumption behaviour of the respective consumer, on the one hand, its identification is possible, and, on the other hand, it is possible to make statements on the present status of each individual consumer by comparing its present individual consumption behaviour with a stored nominal value or with a tolerated range of nominal values.
There still is a need for a method of optimizing a chronological development of consumption of electric power by a group a different consumers with regard to a supply of electric power which includes electric power from at least one wind or solar power generator as well as electric power which is bi-directionally exchanged with a storage for electric energy and/or a public power grid, by which a consumption of electric power is optimized according to the different desires of a user of the consumers but always in a technically defined way. This optimization may be an optimization with regard to a local use of the electric power from the power generator such that a connected public power grid is only utilized to a minimum extent and ideally not needed at all. The optimization may alternatively or additionally also be made with regard to one or several other criteria, like for example a maximum usage of electric power from regenerative power sources, an ecologically sensible power consumption or low energy cost.